Indium tin oxide (ITO) films have been widely used in the technical field of flat panel display, for they are transparent to visible light and have good conductivity, high reflectivity to infrared light, and the like.
Currently, the major method for preparing ITO pattern mainly comprises processes of film formation, exposure, etching, stripping, annealing and the like. FIG. 1 shows the flow diagram of a prior method for preparing a polycrystalline ITO pattern. As shown in FIG. 1, this method comprises:
Step 101: depositing an amorphous ITO film on a base substrate;
Step 102: performing the patterning process to the amorphous ITO film;
Step 103: annealing the amorphous ITO film having a predetermined pattern by heating, so as to convert the amorphous ITO film into a polycrystalline ITO film.
FIG. 2 is a schematic diagram showing an amorphous ITO film deposited on a base substrate. As shown in FIG. 2, an amorphous ITO film 2 with uniform thickness is deposited on a base substrate 1 by Physical Vapor Deposition (hereinafter referred to as PVD).
FIGS. 3a-3c are schematic diagrams showing the patterning processes of the amorphous ITO film, wherein FIG. 3a is a schematic diagram showing a state in which the photoresist is coated on the amorphous ITO film, and exposing and developing has been performed thereafter; FIG. 3b is a schematic diagram showing a state in which wet etching is performed to the amorphous ITO film; FIG. 3c is a schematic diagram showing a state of the amorphous ITO film after stripping. As shown in FIGS. 3a-3c, in step 102, the etching of the amorphous ITO film 2 is completed by patterning process so as to form the amorphous ITO film into a predetermined pattern, and then the photoresist 3 on the amorphous ITO film is stripped by a photoresist stripping solution.
FIG. 4 is a schematic diagram showing a polycrystalline ITO obtained from the amorphous ITO of FIG. 3c by heat-annealing treatment. As shown in FIG. 4, the amorphous ITO pattern is converted to a polycrystalline ITO pattern 4 by performing heat-annealing treatment of the amorphous ITO of FIG. 3c, wherein the heat-annealing treatment generally comprises heating at 200 to 300° C. for 20 to 30 minutes and then cooling for 4 to 10 minutes, so as to convert the amorphous ITO into a polycrystalline ITO.
It can be seen from the above that, many kinds of organic solvents are used in the patterning in this method for preparing polycrystalline ITO pattern, and the conversion of the amorphous ITO into polycrystalline ITO involves heat-annealing. This method involves many disadvantages such as complicated processes, strict operation condition, long production period and high cost. Moreover, the organic solvents used in this method are difficult to deal with and contaminates the environment, and said heat-annealing consumes long time while heating may affect other components in the display device.